Resonant Enhancement of Ground State H$_{2}^{+}$ Formation in Low Energy Charge Transfer between Protons and H$_2$*

We investigated the charge transfer (CT) from an H$_{2}$ or D$_{2}$ target to various fast atomic/molecular ions for a wide span of collision energies in the laboratory frame (eV to keV). Vibrationally resolved cross sections have been obtained on a relative scale, by dissociative charge transfer of the product H$_{2}^{+}$ ions with potassium atoms, and 3-D imaging of the fragments. An absolute value of the total CT cross section has been inferred from the measured ratio of the CT yield for protons and H$_{2}^{+}$, combined with the recommended H$_{2}^{+} +$H$_{2}$ cross section (ORNL). Our results on the (H$_{2}$, H$^{+}$) system benchmark state-to-state calculations at 10eV and above (Phys. Rev. A \textbf{75} 032703, 2007 and J. Phys. B \textbf{42}, 105207 2009). In particular, they confirm the vibrational excitation mechanism responsible for the resonance at 50eV, characterized by a dominant population of the ground vibrational state of H$_{2}^{+}$. The spectra for the isotopic system (D$_{2}$, H$^{+}$) will be also presented along with the results of CT performed with H$_{2}^{+}$ and D$_{2}^{+}$ projectiles.